A reactor is generally provided with a wire and a magnetic core, and an inductance is obtained by constituting a coil of which the wire is wound around the core. Conventionally, a reactor is employed in a step-up circuit, an inverter circuit, and an active filter circuit or the like. As such reactor, there has been often employed the one in which a core and a coil wound around the core are accommodated in a case made of a material such as a metal together with other insulation members or the like. In addition, in a reactor employed in a step-up circuit for vehicle-mounting, for example, two independent coils, each of which is formed by a predetermined winding diameter and the number of windings, are formed in parallel to each other in order to obtain a high inductance value in a high current flow area, and there are employed the coils structured to be linked (connected) with each other so that the directions of currents that flow through the parallel coils are opposite to each other.
As one example of the prior art of the coils described above, there is known the one in which the abovementioned two coils are formed by their individual wires, and end parts of the wires on the linking sides are connected to each other by welding them via a communication terminal (refer to Patent Document 1, for example). In addition, as another example of the prior art, there is known the one of the construction that: two coils in the same winding direction arranged in parallel to each other are formed by edgewise winding of one flat wire; and a linking part of the flat wire acting between the aforementioned two coils in series with each other is double-folded along a longitudinal direction so as to be included in an external form exerted by an end face of each of the coils (refer to Patent Document 2, for example).
In addition, techniques of integrally forming two coils by means of a linking part are disclosed in Patent Documents 3 to 6. Further, techniques of bending and processing the two coils that are integrally formed by means of the linking part from one wire rod are disclosed in Patent Documents 7 and 8.    Patent Document 1: Japanese Patent Application Laid-open No. 2003-124039    Patent Document 2: Japanese Patent Laid-open No. 3737461    Patent Document 3: Japanese Patent Laid-open No. 3398855    Patent Document 4: Japanese Patent Application Laid-open No. 2005-57113    Patent Document 5: Japanese Patent Laid-open No. 2000-195725    Patent Document 6: International Patent Application Publication No. WO 2007/132558    Patent Document 7: Japanese Patent Laid-open No. 3640207    Patent Document 8: Japanese Patent Application Laid-open No. 2005-93852